Wastewater purifying apparatus

ABSTRACT

To purify wastewater discharged from lavatories ( 3 ), a wastewater purifying apparatus having a shell contact aeration chamber ( 6, 7 ) placed with shell microbial carrier members ( 15 ), the wastewater being fed to and purified in the shell contact aeration chamber ( 6, 7 ). Shells whose mother-of-pearl layer on the inner surface (b) is at least removed are used as the microbial carrier member ( 15 ).

TECHNICAL FIELD

The present invention relates to a wastewater purifying apparatus whichcan process swiftly and efficiently wastewater containing humanexcrement discharged from lavatories and the like.

BACKGROUND ART

Heretofore, as described, for example, in Japanese Unexamined PatentPublication No. 9-37996, advanced wastewater processing apparatuses thatefficiently process wastewater containing human excrement dischargedfrom lavatories or the like by aerating the wastewater in an aerationchamber in the presence of oyster shells as microbial carriers and sendthe processed water for reutilization as, e.g., flushing water of flushwater closets have been known. The advanced wastewater processingapparatus, having an aeration chamber containing microbial carriers madeof oyster shell, has advantages in that acidified wastewater can beneutralized by calcium carbonate which become dissolved into thewastewater from the oyster shell, and the wastewater can be purifiedmore efficiently due to increased efficiency of aeration and biologicaldigestion of the wastewater on the surface of the oyster shells.

However, when the oyster shell is used as the microbial carrier in theaeration chamber of the advanced wastewater processing apparatus above,there has been pointed out a problem of a prolonged start-up period,i.e., in that only after a predetermined period from the initial date ofoperation of the advanced wastewater purification apparatus, the fullpotential of the apparatus for neutralization and decomposition andpurification of the wastewater can be exerted.

In view of the above problem, the present invention has been worked out,and an object of the present invention is to provide a wastewaterprocessing apparatus which does not require a prolonged start-up periodand can effectively purify wastewater.

DISCLOSURE OF THE INVENTION

The present invention is directed to a wastewater purifying apparatushaving a shell contact aeration chamber placed with microbial carriershells. Wastewater is fed to and purified in the shell contact aerationchamber. Shells whose mother-of-pearl layer on the inner surface is atleast removed are used as microbial carrier. A shell whose porousprismatic layer is exposed owing to the removal of the mother-of-pearllayer on the surface has an excellent function as microbial carrier tobe used for purification of wastewater because it has a high affinity tomicroorganisms and the like which purify wastewater, and it can easilybecome dissolved into the wastewater.

Additionally, the present invention is directed to a wastewaterpurifying apparatus further provided with an activated carbon adsorptionchamber packed with coal-based activated carbon and arranged downstreamof the shell contact aeration chamber. In such an arrangement, treatedwastewater purified in the aeration chamber described above istransferred to the activated carbon adsorption chamber where thewastewater is effectively decolorized.

Additionally, the present invention is directed to a wastewaterpurifying apparatus further provided with a denitrification chamberarranged upstream of the shell contact aeration chamber placed with abioreactor including a membranous container containing a hydrogen donor.In such an arrangement, ammonia components in the wastewater areconverted, via nitrous acid and nitric acid, to nitrogen gas and thusremoved from the wastewater by denitrification of denitrifying bacteriaadherent to the surface of the membranous container through the use ofthe hydrogen donor.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view showing a wastewater purifying apparatus ina first embodiment of the present invention;

FIG. 2 is a diagram illustrating the wastewater purifying apparatus ofthe first embodiment;

FIG. 3 is a sectional view illustrating a shell structure;

FIG. 4 is a sectional view illustrating a structure of a shell used inthe wastewater purifying apparatus;

FIG. 5 is a perspective view showing a specific arrangement of acirculation system;

FIG. 6 is a diagram illustrating a wastewater purifying apparatus in asecond embodiment of the present invention; and

FIG. 7 is a diagram illustrating a wastewater purifying apparatus in athird embodiment of the present invention.

BEST MODE FOR CARRYING OUT THE INVENTION

The present invention will be described more in detail referring to thedrawings attached.

FIG. 1 and FIG. 2 illustrate a wastewater purifying apparatus in a firstembodiment of the present invention. The wastewater purifying apparatuscomprises a wastewater processing tank 1, and a storage tank 2 forstoring purified wastewater from the processing tank 1, both of whichare made of a material such as steel, aluminum alloy, stainless steel,plastic, prestressed concrete, armored concrete, fiber reinforcedplastic, etc., and usually used as they are laid underground.

The wastewater processing tank 1 further comprises, a settling chamber 4for separating solids in wastewater discharged, via an influent pipe 3a, from a lavatory 3, an aeration chamber 5 for aerating the clarifiedwastewater transferred from the settling chamber 4, first and secondshell contact aeration chambers, 6 and 7 for further aerating theprocessed wastewater transferred from the aeration chamber 5, asedimentation filtration chamber 8 for sedimentation and filtration ofthe processed wastewater transferred from the second shell contactaeration chamber 7, and an activated carbon adsorption chamber 9 fordecolorizing the supernatant processed wastewater transferred from thesedimentation filtration chamber 8.

In the settling chamber 4, papers and other bulky foreign particles inthe wastewater are separated by sedimentation, and the solid-freeclarified wastewater is transferred via a conduit tube 10 to thedownstream aeration chamber 5, and the settling chamber 4 is fitted witha baffle plate 11 for preventing washout of suspended solids into theaeration chamber 5. The solid sediments in the settling chamber 4, bythe way, are withdrawn periodically, (for example, once a year), andseparately processed.

In the aeration chamber 5, are arranged a contact zone placed with knownplastic microbial carriers 12, and an aeration nozzle 14 beneath thecontact zone for diffusing air supplied from a blower 13. The clarifiedwastewater in the aeration chamber 5 transferred from the settlingchamber 4 is agitated by the air released from an aeration nozzle 14,and excrements in the clarified wastewater are decomposed bymicroorganisms living adherent to the surface of the plastic microbialcarriers 12.

In each of the first and second shell contact aeration chambers, 6 and7, are arranged microbial carrier members 15, a mesh bag packed withmicrobial carrier shells of shellfish such as oyster, scallop, Sakhalinsurf clam, pearl shell, clam, fresh water clam, short-necked clam,Chinese mecta, mussel, top shell, giant clam, etc., or fossil shell, andan aeration nozzle 16 beneath it for releasing the air supplied from theblower 13.

The shell contains calcium carbonate as a major component and calciumphosphate, magnesium carbonate, etc., as minor components, and, as shownin FIG. 3, has a three-layered structure comprising an outer layer ofshell epidermis a, an inner layer of mother-of-pearl layer b, and anintermediate layer of prismatic layer c. As shown in FIG. 4, themicrobial carrier member 15 described above is a bag packed with shellsnot having the mother-of-pearl layers b.

Examples of the process to remove the mother-of-pearl layer b from shellinclude a method to scrape off the mother-of-pearl layer b by means of aproper machine tool, a method to leave the shell at the water's edge ofseashore for a period of about 1 year and allow natural erosion of themother-of-pearl layer b, a method to dissolve the mother-of-pearl layerb by the use of a chemical, such as hydrochloric acid and the like, anda method to scrape off the mother-of-pearl layer b by agitating numbersof shells in a mixer and thus making mutual grinding among the shells.When the mother-of-pearl layer b was removed either by the naturalerosion method or the agitation method described above, part of theshell epidermis is also to be removed along with the mother-of-pearllayer b.

The treated wastewater in the first shell contact aeration chamber 6transferred as the overflow of the aeration chamber 5 is agitated by theair released from the aeration nozzle 16 and the excrements in thewastewater are decomposed by microorganisms living adherent to thesurface of the shell microbial carrier member 15. Subsequently, thewastewater in the second shell contact aeration chamber 7 transferred asthe overflow of the first shell contact aeration chamber 6 is agitatedby the air released from the aeration nozzle 16, and the excrements inthe wastewater are further decomposed by microorganisms living adherentto the surface of the shell microbial carrier member 15, andsubsequently transferred as the overflow to the sedimentation filtrationchamber 8.

In the sedimentation filtration chamber 8 having a filter 17 packed withporous zeolites, impurities in the treated wastewater transferred fromthe second shell contact aeration chamber 7 settle down, bringingseparation of the sediment and the supernatant, and smaller impuritieswhich remain in the supernatant is then filtrated through the filter 17,and the filtrated supernatant wastewater is transferred, via a conduittube 18, to the activated carbon adsorption chamber 9 As shown in FIG.5, in the activated carbon adsorption chamber 9 are arranged anadsorption column 21 wherein two partition plates 19 and 20, having aplurality of holes are placed at the upper and lower positions thereof,and an activated carbon container 22 between the two partition plates 19and 20, and the circulation system including circulation pipes 23 and acirculation pump 24 for withdrawing the wastewater in the activatedcarbon adsorption chamber 9 and for pumping into the lower portion ofthe activated carbon container 22. The activated carbon container 22includes a bag made of fabric or the like, and a coal-based activatedcarbon to be placed therein. The wastewater pumped into the lowerportion of the activated carbon container 22 by the circulation system25 flows through the adsorption column 21, and circulates back into theactivated carbon adsorption chamber 9, whereby colored components areadsorbed by the coal-based activated carbon in the activated carboncontainer 22, and thus the wastewater is decolorized efficiently.

As shown in FIG. 1, part of the purified wastewater decolorized in theactivated carbon adsorption chamber 9 as described above, is supplied toa feed tank 29 of the lavatories 3 by a water supplier 28 including apump 26 and a feed pipe 27, and the other part is transferred, via aconduit tube 30, to the storage tank 2 for storage.

As described above, the use of shell such as oyster shell, of which atleast the inner mother-of-pearl layer b is removed and the porousprismatic layer is exposed, as the microbial carrier member 15 to beused in the first and second shell contact aeration chambers 6 and 7 ofthe wastewater purifying apparatus, makes it possible to increase anaffinity of the microbial carrier member 15 for microorganismsdecomposing the excrements in the wastewater in the first and secondshell contact aeration chamber 6 and 7 withdrawn from the filtrationchamber 5, and thus to propagate the microorganisms adequately. That is,by the microorganisms propagated on the surface of the porous prismaticlayer c, excrements in the wastewater can be decomposed and thewastewater purified more efficiently.

The use of the shell as the microbial carrier member 15 has anadditional advantage in that it is possible to make the microorganismsexercise the decomposition and other functions from the beginning ofoperation after installment of the wastewater purifying apparatus, thuspreventing possible environmental pollution which may occur during thestart-up period when the purified wastewater processed by the wastewaterpurifying apparatus is discharged outside, and to utilize water resourcemore efficiently by reutilizing the purified water as flushing water ofthe lavatories 3.

Additionally, when the wastewater is acidified as a result of aerationof the wastewater in the aeration chamber 5 and in the first and secondshell contact aeration chambers 6 and 7, calcium carbonate becomesdissolved from the shell neutralizing the wastewater. That is, the shellof which the mother-of-pearl layer b is scraped off has an advantage inthat it can neutralize the acidified wastewater more efficiently due toits higher tendency to be dissolved in the wastewater.

Since the wastewater is neutralized in the first and second shellcontact aeration chambers 6 and 7 as described above, protozoan such asheliozoan and coelenterates can be developed and proliferated in largequantity. Therefore, by extinguishing bacteria such as Escherichia coliand the like present in the wastewater through predation by theprotozoa, it becomes possible to efficiently prevent bacterialcontamination of the purified wastewater from the wastewater purifyingapparatus.

Further, when the wastewater contains phosphorus components, thephosphorus components can be reacted with calcium carbonate to yieldcalcium phosphate. Thus, the use of the shell as the microbial carriermember 15 has an additional advantage in that the calcium phosphate thusformed is adsorbed on the activated carbon in the activated carboncontainer 22 arranged in the activated carbon adsorption chamber 9, andcan be recovered for use as a fertilizer or the like.

Meanwhile, part of the calcium phosphate in the wastewater precipitatesin the sedimentation filtration chamber 8 and is adsorbed in the filter15, and the other part is adsorbed on the activated carbon in theactivated carbon adsorption chamber 9. For the purpose of removing aminute amount of the phosphorus components which remains in thewastewater, it is desirable to place an additional phosphorus adsorptioncolumn placed with the shells such as oyster shell and the like in theactivated carbon adsorption chamber 9.

To evaluate wastewater purification performance of the wastewaterpurifying apparatus shown in FIG. 1 and FIG. 2, experiments to determinethe wastewater purification performance have been carried out, inInventive Example wherein an oyster shell of which the mother-of-pearllayer b was scraped off was used as the microbial carrier member 15 inthe first and second shell contact aeration chambers 6 and 7,Comparative Example 1 wherein a known plastic microbial carrier is used,and Comparative Example 2 wherein an untreated oyster shell having themother-of-pearl layer b was used as the microbial carrier, and theresults are shown in the following TABLES 1 to 7.

TABLE 1

TABLE 2

TABLE 3

TABLE 4

TABLE 5

TABLE 6

TABLE 7

TABLE 1 shows measured values of pH concentration of the purifiedwastewater, and indicates that pH of the purified wastewater was in aneutral range all year in the Inventive Example, while pH thereof had atendency to become lower (acidic) in the Comparative Examples 1 and 2.The data in TABLE 1 indicate that by the use of the oyster shell ofwhich the mother-of-pearl layer b is scraped off as the microbialcarrier member 15, it is possible to prevent effectively theacidification of the purified wastewater.

TABLES 2 to 4 show, respectively, measured values of the variation ofsuspended solids (SS, mg/L), BOD (biochemical Oxygen Demand, mg/L) andCOD (Chemical Oxygen Demand, mg/L) of the purified wastewater inInventive Example and Comparative Examples 1 and 2, and indicate that bythe use of oyster shells of which the mother-of-pearl layer b is scrapedoff as the microbial carrier member 15, it is possible that excrementsin the wastewater can be effectively decomposed and the wastewater canbe purified from the beginning of operation after installment of thewastewater purifying apparatus.

TABLE 5 shows measured values of the variation of coliform bacteriacount of the purified wastewater, and indicates that by the use ofoyster shells of which the mother-of-pearl layer b is scraped off as themicrobial carrier member 15, the bacteria count of the wastewater can bedecreased effectively.

TABLES 6 and 7 show, respectively, measured values of the variation oftotal amount of phosphorus components (T-P) and amount of phosphoruscomponents as phosphate (P04-P) in the purified wastewater, and indicatethat by the use of oyster shells of which the mother-of-pearl layer b isscraped off as the microbial carrier member 15, the amount of phosphoruscomponents and of phosphate in the wastewater can be decreasedeffectively.

In the first embodiment of the invention, an activated carbon adsorptionchamber 9 containing an activated carbon container 22 packed with acoal-based activated carbon is arranged downstream of the first andsecond shell contact aeration chambers 6 and 7, and thus the wastewaterprocessed in the first and second shell contact aeration chambers 6 and7 can be decolorized effectively in the activated carbon adsorptionchamber 9.

Experiments to determine the variation of color of the purified waterwere carried out in Inventive Example wherein a coal-based activatedcarbon was packed in the activated carbon container 22, and ComparativeExample wherein a palm shell activated carbon was packed, and theresults are shown in TABLE 8. The data indicate that the use of thecoal-based activated carbon provides a longer period of favorabledecolorization than the use of the palm shell activated carbon.

TABLE 8

In particular, an arrangement described in the first embodiment, whereinthe wastewater in the activated carbon adsorption chamber 9 is withdrawnand pumped into the lower portion of the activated carbon container 22,and circulated back into the activated carbon adsorption chamber 9 hasan advantage in that the color components in the wastewater can beadsorbed more efficiently on the coal-based activated carbon in theactivated carbon container 22 and thus the decolorization of thewastewater can be increased.

An arrangement of the first embodiment wherein the filtration chamber 5placed with plastic microbial carrier 12 is placed upstream of the firstand second shell contact aeration chambers 6 and 7, i.e., partiallypurified wastewater being fed to the first and second shell contactaeration chambers 6 and 7, has an advantage in that it can effectivelyprevent defacement and disappearance by dissolution of the shells suchas oyster shells or the like which are placed in the first and secondshell contact aeration chambers 6 and 7.

Especially, as shown in FIG. 6, an arrangement wherein an additionalsedimentation chamber 5 a for the sedimentation of sludge in the aeratedwastewater transferred from the aeration chamber 5 is placed between theaeration chamber 5 and the first shell contact aeration chamber 6, candecrease more efficiently defacement and disappearance by dissolution ofthe shells placed in the first and second shell contact aerationchambers 6 and 7.

In the second embodiment shown in FIG. 6, between the first shellcontact aeration chamber 6 and the second shell contact aeration chamber7 is arranged a denitrification chamber 50, wherein bioreactors,membranous containers in the shape of bags made of a membrane materialsuch as polyethylene or the like containing a hydrogen donor, i.e., anorganic hydrocarbon such as methanol and the like are placed.

In the wastewater purifying apparatus fitted with the first and secondshell contact aeration chambers 6 and 7, when the denitrificationchamber 50 fitted with the bioreactors 51 is placed upstream of thesecond shell contact aeration chamber 7, ammonia components in thewastewater can be removed by being converted, via nitrous acid andnitric acid, to nitrogen gas by the denitrification action of thedenitrifying bacteria adherent to the surface of the membranouscontainers constituting the bioreactor 51 utilizing the hydrogen donor,and therefore amount of ammonia and nitrogen components in thewastewater can be markedly reduced.

The arrangement above has also an advantage in that when an excessamount of the hydrogen donor are released from the bioreactor 51, thehydrogen donor can be decomposed by calcium carbonate being dissolvedfrom the shells in the second shell contact aeration chamber 7. As thedenitrifying bacteria are anaerobic, it is not desirable to supply alarge amount of air into the denitrification chamber 50, however it ispossible to increase denitrification efficiency of the denitrifyingbacteria by supplying a limited amount of air only sufficient foragitation of the wastewater in the denitrification chamber 50 throughthe aeration nozzle 16.

Instead of arranging a denitrification chamber 50 between the first andsecond shell contact aeration chambers 6 and 7 as described in theembodiment above, the denitrification chamber 50 may be placed upstreamof the first shell contact aeration chamber 6. In the first and secondembodiments of the invention, an arrangement of a processing tank 1comprising a settling chamber 4, an aeration chamber 5, a sedimentationchamber 5 a, first and second shell contact aeration chambers 6 and 7, adenitrification chamber 50, a sedimentation filtration chamber 8, and anactivated carbon adsorption chamber 9 is described, but chambersnecessary as components for the wastewater purification apparatus and anarrangement of the chambers are not limited to the embodiments above,and a variety of modifications are possible within the scope of thepresent invention.

As shown in FIG. 7, the wastewater processing apparatus may, forexample, have an arrangement including the following two separatelymanufactured tanks, a first processing tank 31 comprising a settlingchamber 4, an aeration chamber 5, and a sedimentation chamber 5 a, and asecond processing tank 32 comprising first and second shell contactaeration chambers 6 and 7, a denitrification chamber 50, a sedimentationfiltration chamber 8, and an activated carbon adsorption chamber 9.Alternatively, by eliminating the first processing tank 31 comprising asettling chamber 4, a filtration chamber 5, and a sedimentation chamber5 a, wastewater discharged form lavatories 3 may be fed directly to thefirst shell contact aeration chamber 6 in the processing tank 32, andprocessed in the first contact aeration chamber 6, the denitrificationchamber 50, the second shell contact aeration chamber 7, thesedimentation filtration chamber 8, and the activated carbon adsorptionchamber 9, in the order.

INDUSTRIAL APPLICABILITY

As described above, the wastewater purifying apparatus is useful fordecomposition of the excrements in wastewater discharged form lavatoriesand the like and for purification of the wastewater, and can exert itsexcellent purification potential from the beginning of operation afterinstallment of the wastewater purifying apparatus and is suitable forsuppressing acidification of the purified wastewater.

What is claimed is:
 1. A wastewater purifying apparatus comprising ashell contact aeration chamber including calcium carbonate based shellsof shellfish for purifying supplied wastewater therein, the shells beingused as microbial carriers with a mother-of-pearl layer on innersurfaces of the shells being removed.
 2. A wastewater purifyingapparatus according to claim 1, further comprising an activated carbonadsorption chamber including coal-based activated carbon and arrangeddownstream of the shell contact aeration chamber.
 3. A wastewaterpurifying apparatus according to claim 1, further comprising adenitrification chamber which is arranged upstream of the shell contactaeration chamber, the denitrification chamber being provided with abioreactor including a membranous container containing a hydrogen donor.4. A wastewater purifying apparatus according to claim 1, wherein theshellfish includes at least one of oysters, scallops, Sakhalin clams,pearl shells, clams, fresh water claims, short-necked clams, Chinesemecta, mussels, top shells, giant clams and fossil shells.
 5. Awastewater purifying apparatus according to claim 1, wherein the shellsare packed in a mesh bag and installed in the shell contact aerationchamber.